Heavy police forces and armored vehicles present in the village of Banjska in Kosovo.
BetaPhoto/Sipa/Shutterstock
Heavy police forces and armored vehicles present in the village of Banjska in Kosovo.
CNN — 

The long fractious ties between Kosovo and Serbia are once again on edge after one of the worst outbreaks of violence in years.

The trigger for the latest flare-up was the killing of a Kosovar police officer and an ensuing shootout at a monastery last weekend, but the roots of the tensions go as far back as the 1990s and the disintegration of the former Yugoslavia.

The White House is concerned, warning of an “unprecedented” build up of advanced Serbian artillery, tanks, and mechanized infantry units near the Kosovo frontier and calling for an “immediate de-escalation.”